Longitudinal and perpendicular recording heads for use with a magnetic storage medium are generally known. Longitudinal recording heads utilize a pair of opposing write poles with their tips in close proximity to each other at the bottom surface of the recording head. The two poles are connected at the top by a yoke, which may be made of a ferromagnetic material similar to that used for the poles. In conventional designs, a coil having multiple turns surrounds the yoke in close proximity to the two opposing poles. When a current is passed through the coil, magnetic flux is induced in the yoke, which produces a magnetic field across a write gap separating the two poles. A portion of the magnetic flux across the write gap passes through the magnetic storage medium, thereby causing a change in the magnetic state within the magnetic storage medium to modify the bits of information on the storage medium. The recording densities possible with longitudinal recording are believed to be limited to approximately 50 to 100 Gbit/inch2 because, at higher recording densities, superparamagnetic effects result in magnetic instabilities within the magnetic storage medium.
Perpendicular recording has been proposed to overcome the recording density limitations of longitudinal recording. Perpendicular recording heads for use with magnetic storage media may include a pair of magnetically coupled poles connected by a yoke. The main write pole has a small bottom surface area while the flux return pole has a large bottom surface area. In conventional designs, a coil having a plurality of turns is located adjacent to the yoke or main write pole for inducing a magnetic field between the write pole and a soft underlayer of the recording medium. The soft underlayer is located below the hard recording layer of the magnetic storage medium and enhances the amplitude of the field produced by the main pole. This in turn allows the use of storage medium with higher coercive force. Consequently, more stable bits can be stored in the medium.
In conventional write head designs, the switching speed limit (non eddy-current limited) occurs when the write head exhibits ferromagnetic resonance (FMR). The presence of underdamped FMR oscillations in the write field may cause distorted write field shapes in the media. Furthermore, the flux transmission velocity through the write head yoke is not necessarily equal to the FMR-limited switching speed.
Also, in conventional writers, the coil is placed relatively far away from the air bearing surface (ABS), and the driving field is predominantly located at the back region where the write poles are connected by the yoke. The writing field that emerges from the pole tips relies on flux transmission through a dispersive medium, which acts to broaden and slow the dynamic magnetization. Even if switching speeds near the ferromagnetic resonance point can be generated, the magnetization will switch fast only where a fast magnetic field exists to drive the magnetization. Therefore, at high data rates, conventional designs may be limited by the dispersion characteristics of the mode propagating through the yokes to the pole tips.
The present invention has been developed in view of the foregoing and to address other deficiencies of the prior art.